U.S. Pat. No. 3,861,745 discloses a portable seat that can be placed upon a wheel chair or any type of chair upon which a person with an amputated leg can sit. The portable seat is provided with a section that is mounted to the seat by a hinge arrangement so that the hinged section can be moved to a leg-supporting position from a nonleg-supporting position and another hinge is operated to maintain the hinged section in the leg-supporting position. This enables the person with an amputated leg to horizontally support the residual limb on the hinged section while sitting on the portable seat to insure proper circulation and knee extension. When the person wants to rise to a standing position, the hinge is operated to move the hinged section to a downward nonleg-supporting position so that the person can now arise from the seat because the hinge section is now out of the way.
While this portable seat is useful to support the residual limb, the seat is bulky because of the hinged section, and the hinged section generally has to be operated by another person. The hinge structure not only includes hinges to hingedly mount the hinged section to the seat, but also another hinge that is locked into one position to maintain the hinged section in a leg-supporting position and a release mechanism is included with the other hinge to unlock it so that the hinged section can be moved to a nonleg-supporting position. This constitutes a complex and expensive portable seat for use by leg amputees.